The invention relates to improved asphalt blocks for use in applications such as roofing and paving. In particular, the invention further provides a reinforcement for asphalt blocks made in molds, and results in the asphalt block maintaining its shape even in hot weather. An additional feature of the invention provides reinforcing moldings located within the asphalt blocks to provide reinforcement and decrease deformation due to asphalt cold flow in warm weather. Another feature of the invention provides polymer moldings to reinforce handling features such as handles and wedges and to generate weaker spots that can contribute to splitting them in halves by knocking the blocks against a surface. A further feature of the invention provides a fume reduction ability when the asphalt block Is melted in the kettle due to the melting down of polypropylene and/or TruMelt formulation moldings inserted in the asphalt package.
In the asphalt industry, one way of transporting asphalt to the users is in the form of individual packages or blocks, which are used often by building contractors as a source of asphalt for roofing and other construction applications. Individual packages of asphalt are often formed at conventional roofing asphalt-processing facilities by pouring molten asphalt into containers made of a metal bottom and paper cylindrical sidewalls. The asphalt is typically poured at temperatures of about 177xc2x0 C. and the packages are allowed to cool for twenty-four hours prior to shipping to users, such as roofing contractors. After removing the paper and metal container, which become waste, the roofing worker places the solid asphalt in a gas-fired melting to melt down the asphalt.
Packages have been developed that eliminate the need to remove or dispose of the container. One type of such a package is disclosed in, e.g., U.S. Pat. Nos. 5,452,800 and 5,307,608, which relate to asphalt packages employing thin polypropylene based film as the sole containment means and methods of manufacture. The disclosure of these patents is herein incorporated by reference.
Another type of consumable asphalt package that has been developed is a moldable container described in U.S. Pat. Nos. 5,733,616 and 5,765,686, the disclosure of which is incorporated by reference herein. The consumable containers molded from compositions comprise asphalt and polymer material. The containers may be of cylindrical or rectangular designs, and may be tapered for stacking and include such features as handholds to facilitate handling and annular protrusions or circumferential ribs to enhance dimensional stability.
Although moldable consumable containers have been attained, which have an advantage of reducing fuming in an asphalt-melting kettle, improvements are especially needed in the lower end traditional asphalt block molding processes, so as to reduce cold flow and aid in handling of the molded asphalt blocks.
Accordingly, an object of the invention is to provide an asphalt block or package that is convenient to handle in manufacture and use. An additional object is to provide a package that is freestanding and strong to withstand deformation due to asphalt cold flow, especially in warm weather. A further object is to provide a container or asphalt block that reliably can be broken in smaller pieces at the job site when it is knocked against a hard surface reducing or eliminating clean-up of small pieces of asphalt. A further object of the invention is to provide a stronger asphalt block that has improved resistance to cold flow in warm weather while also reducing emissions at the kettle when melted for lower end asphalt blocks produced in traditional mold processes. These and other objects are achieved by the asphalt blocks according to the invention.
An aspect of the invention may be used In containers such as traditional asphalt molds, i.e. nonconsumable. These traditional molds are typically metal, plastic, cardboard or combinations of such materials and are used to produce asphalt blocks. The blocks produced have severe problems of cold flow. An embodiment of the invention which directly improves the cold flow deformation in asphalt blocks made in nonconsumable molds comprises a retaining means such as a liner or band of polymer film used inside the mold. The liner has a thickness of from about 2-5 mils and lines the mold In which the asphalt is poured. The liner may be used as a sheet or film lining only the side walls or edges of the mold or it may be used to line the entire inner surface of the mold. In another embodiment, the retaining means used to improve the cold flow comprises slabs, bars or beams of polymer. In these embodiments, the retainer comprises up to 100% total polymer(s). In a particularly preferred embodiment, the polymer is polypropylene, polyethylene, ethylene vinyl acetate, EMA, or a polymer in combination with asphalt such as Trumelt(trademark) (see U.S. Pat. No. 5,733,616).
In one embodiment, an asphalt block or package of the invention comprises a breakage means which comprises wedges or molded parts that are added after the lining film at the bottom of the mold or container. The breakage means may also be used in a mold that does not contain a lining firm. The wedges or parts are added before or after the asphalt is poured into the mold and are oriented such that the sharp or more narrow edge aims toward the interior of the block. The wedges or molded parts are made of polymers such as polypropylene or any other polymer which does not significantly detract from the strength or performance of the asphalt. The breakage means of the invention allow for the production of larger asphalt blocks that may be broken at the site of use. In a preferred embodiment the wedges or molded parts also reduce gaseous emissions when the blocks are melted.
In another embodiment a polymer film retaining means is added inside the mold prior to addition of the asphalt. In a preferred embodiment a reinforcing polymer film band may be placed, glued, adhered or stamped in the inside or outside of the polymer film. Another embodiment uses the polymer film band without the use of the polymer film liner. The polymer film band may be used as a retainer in containers such as consumable containers and nonconsumable molds.
A further embodiment for reinforcing the block so as to reduce cold flow problems comprises the use of reinforcing moldings or beams. The moldings or beams are used along the sides of the mold and are placed inside the mold. The beams may be used in applications using the polymer film liner in consumable or nonconsumable molds.
An additional embodiment Involves the use of polymer moldings inserted or molded into the molds to shape handles in the resulting asphalt blocks.
Other features and advantages of the invention will become apparent from the detailed description in conjunction with the drawings.